I tend to agree with the MS engineers here. I've found out only yesterday that the FPU/math library is not entirely deterministic in some calculations (including square roots and trigonometry, typical 3d stuff), so I think worrying about serialization/deserialization is useless.
I disagree, it is certainly possible to serialise/deserialise exactly, glibc manages it OK, so I see no reason why MS can't. Square roots are exactly-rounded under IEEE arithmetic BTW, as are the usual + - * / operators: it's the functions that may return transcendental values (cos sin exp, pow) which can never give exact answers purely as a matter of principal: although in practice most implementations are last-bit-correct for the vast majority of inputs.
Do you have example code / pointers to documentation for that? I've always been under the impression that basic math is deterministic regardless of IEEE compliance, and would really like to know if/where there are cases where that doesn't hold.
I assume you've read "What Every Computer Scientist Should Know About Floating-Point Arithmetic" at http://docs.sun.com/source/806-3568/ncg_goldberg.html ? John.